The present invention relates to an exposure apparatus used for a semiconductor manufacturing process, and a projection exposure apparatus that projects and transfers a reticle pattern onto a silicon wafer. The present invention is suitable for an extreme ultraviolet (“EUV”) exposure apparatus that uses EUV light with a wavelength of about 13 to 14 nm as exposure light and a mirror optical system for projection exposure in vacuum.
A prior art example will be described with reference to FIGS. 10 and 11. 101 uses a YAG solid laser etc. serving as an excitation laser for exciting gasified, liquefied or atomized-gasified light-source material atoms into plasma for light emissions by irradiating a laser beam onto the light-source material.
102 is a light-source emitting part that maintains an internal structure to be vacuum. 102A is a light source A of an actual emitting point in an exposure light source.
103 is a vacuum chamber that contains an exposure apparatus, and can maintain the vacuum state using a vacuum pump 104.
105 is an exposure light introducing part (or an illumination optical system) for introducing exposure light from the light-source emitting part 102, which includes mirrors A (or 105A) to D (or 105D), to make uniform and shape the exposure ray.
106 is a reticle stage, and its movable part is mounted with a reflective original form 106A that produces a pattern to be exposed.
107 is a reduction projection mirror optical system that reduces and projects an exposure pattern reflected from the original sequentially form through mirrors A (or 107A) to E (or 107E) at a predefined reduction ratio.
108 is a position-controlled wafer stage for positioning a wafer 108A, as a Si substrate, into a predetermined exposure position so that the wafer stage can be moved along six axes directions, i.e., moved in the XYZ directions, tilted about the XY axes, and rotated around the Z axis. The pattern on the original form 106A is to be reflected, reduced and projected onto the wafer 108A.
109 is a reticle stage support for supporting the reticle stage 105 on an apparatus installation floor. 110 is a projection optical system body for supporting the reduction projection mirror optical system 107 on the apparatus installation floor. 111 is a wafer stage support for supporting the wafer stage 108 on the apparatus installation floor.
The reticle stage, the reduction projection mirror optical system, and the wafer stage, are supported by the reticle stage support, the projection optical system body and the wafer stage support, respectively. These include means (not shown) for measuring relative positions so as to continuously maintain their predetermined configuration.
A mount (not shown) for violation isolation from the apparatus installation floor is provided on the reticle stage support 109, the projection system body 110, and the wafer stage 111, which are provided independently.
112 is a reticle stocker that includes a storage container that temporarily stores, in an airtight condition, plural original forms 106A as the reticles supplied from the outside to the inside of the apparatus and suitable for different exposure conditions and patterns.
113 is a reticle changer for selecting and feeding a reticle out of the reticle stocker 112.
114 is a reticle alignment unit that includes a rotary hand that can travel along the XYZ axis directions and can rotate about the Z axis. The reticle alignment unit 114 receives the original form 106A from the reticle changer 113, rotates it by 180°, and feeds it to a reticle alignment scope 115. The reticle alignment scope 115 is provided at the end of the reticle stage 106 for fine movements of the original form 106A rotating about the XYZ-axes and aligns the original form 106A with an alignment mark 115A provided on the reduction projection mirror optical system 107. The aligned original form 106A is chucked on the reticle stage 106.
116 is a wafer stocker that includes a storage container for temporarily storing plural wafers 108A from the outside to the inside of the apparatus.
117 is a wafer feed robot for selecting a wafer 108A to be exposed, from the wafer stocker 116, and feeds it to a wafer mechanical pre-alignment temperature controller 118 that roughly adjusts feeding of the wafer in the rotational direction and controls the wafer temperature within controlled temperature in the exposure apparatus.
119 is a wafer feed hand that feeds the wafer that has been aligned and temperature-controlled by the wafer mechanical pre-alignment temperature controller 118 to the wafer stage 108.
120 and 121 are gate valves used as mechanisms for opening and closing a gate for supplying the reticle and wafer from the outside of the apparatus. 122 is also a gate valve that uses a diaphragm to separates spaces among the wafer stocker 116, the wafer mechanical pre-alignment temperature controller 118, and the exposure in the apparatus. The gate valve 122 opens and closes only when moving the wafer 108A in and out of the apparatus.
Such a separation using the diaphragm can minimize a capacity to be temporarily released to the air when the wafer 108A is fed in from the outside of and fed out of the apparatus, and quickly form a vacuum equilibrium state.
Thus, when the conventionally structured exposure apparatus positions the mirrors A to E relative to the mirror barrel 107F as shown in FIG. 11, the mirror deforms by its own weight (in a direction depicted by the arrow in the drawing). Mirrors used for an exposure apparatus that uses the EUV light are required to maintain such strict surface shape precision as 1 nm or smaller, but this precision cannot be guaranteed when the mirror deforms due to its own weight.
When the mirror's surface shape precision deteriorates in the projection optical system, it deteriorates imaging performance, increases aberration, and lowers light intensity.
When the mirror's surface shape precision deteriorates in the illumination optical system, it produces lowered and non-uniform light intensity on the mask. In particular, when a light-source mirror deforms due to its own weight, the light intensity deteriorates, which causes insufficient condensing.